A. Field of the Invention
The invention relates to an energy savings device or method that can be applied to a resistive or an inductive load regardless of the impedance or inductance of the load. More particularly, the invention relates to a reactive load dimming device that is mounted in series with a resistive or an inductive load and that has access for power and operation to one side of an electrical line supplied to the load. A fluorescent light fixture or a motor for a fan or other device, for example, can be controlled by way of an energy savings device or method according to the invention.
B. Description of the Related Art
The ability to control illumination levels is strongly desired, especially due to the rising energy costs. Such ability to control illumination levels is very important for establishments that require a great deal of lighting, such as restaurants and offices.
Lighting levels that are higher than necessary not only result in a higher energy costs associated with the lighting, but also can increase air conditioning costs due to the excess heat provided by the lighting fixtures. Fluorescent light fixtures output less heat than incandescent light fixtures for equivalent illumination, and thus they are becoming more popular with offices or other commercial establishments.
There currently exist various types of dimmer devices that can be used in order to control the amount of light output by fluorescent lights. One type utilizes a complex electronic ballast which first converts the applied AC line voltage to DC, then switches the applied tube voltage at high frequency. The resulting power-to-light output efficiency is hampered by this additional manipulation. This type requires an expensive fixture replacement and rewiring to the wall switch. Simplistic phase control devices will not provide satisfactory results when controlling a magnetic ballast fluorescent fixture.
FIG. 1A shows the connections of a conventional fluorescent dimmer device or controller 100, which is provided between a line and a load. The load is shown as a light fixture 110, which may be a fluorescent tube and associated ballast, for example. As shown in FIG. 1A, the conventional controller 100 needs access to both sides (line 102 and neutral 104) of an AC power input, in addition to the load. Since connectivity to the neutral line 104 is not always available at a light switch box, conventional fluorescent controllers may require expensive re-wiring to be installed.
The problem with using such a conventional dimmer circuit for a fluorescent lighting fixture is that the conventional dimmer circuit cannot modulate reactive loads. Reactive loads react with the controller, thereby producing oscillations that then cause surges of voltage and current, which are both unpredictable and uncontrollable. With such control being applied to a fluorescent light fixture, the typical result is a non-harmonic type of flickering, which frequently takes the light from zero output to maximum output and to values in between. Such flickering is visually (and also audibly) discomforting, and may even be unhealthful to people who are near the flickering fluorescent light (for example, it may cause headaches due to having to view the undesirable light flickering).
As explained earlier, a controller such as the one shown in FIG. 1A can be used to control a fluorescent light without causing significant flickering, but such a controller requires fairly substantial installation costs, since they cannot be installed at a light switch box (where a neutral line is not typically provided), but rather have to be installed very close to the ballast (e.g., in the ceiling of a room, where a neutral line is provided).
U.S. Pat. No. 5,043,635 to Talbott et al. describes a two-line power control device for dimming fluorescent lights, which does not require to be coupled to a neutral line. Accordingly, the Talbott et al. device can in theory be installed at a light switch box. However, due to the analog structure and the various components described in the Talbott et al. device, such a device is very difficult to manufacture, and also such a device is very difficult to manufacture in a small size. Thus, it is not feasible to install such a device in a light switch box, given the bulkiness as well as the transformer configuration of the Talbott et al. device.
The present invention is directed to an apparatus and a method for controlling an amount of power supplied to a resistive or inductive load by modulating a period of time that current flows through the load.
According to one aspect of the invention, there is provided an energy savings device for an inductive or resistive load that is powered by an input AC voltage waveform. The device includes a setting unit for setting a desired power operating level for the load. The device also includes a microprocessor configured to receive a signal from the setting unit indicative of the desired power operating level for the load, to determine a phase delay to be provided to an output AC voltage waveform that is to be provided to the load, and to output a control signal as a result thereof. The device further includes an active element provided between a line that provides the input AC voltage waveform and the load, the active element receiving the control signal and turning off and on at predetermined times in accordance with the control signal, so as to create the output AC voltage waveform from the input AC voltage waveform.
According to another aspect of the invention, there is provided an energy savings method for an inductive or resistive load that is powered by an input AC voltage waveform. The method includes setting a desired power operating level for the load. The method further includes receiving a signal indicative of the desired power operating level for the load, and determining a phase delay to be provided to an output AC voltage waveform that is to be provided to the load, and to output a control signal as a result thereof. The method also includes receiving the control signal, and, in response thereto, turning an active element off and on at predetermined times in accordance with the control signal, so as to create the output AC voltage waveform from the input AC voltage waveform. The active element is disposed between a line carrying the input AC voltage waveform and the load.
According to yet another aspect of the invention, there is provided a computer program product for providing energy savings for an inductive or resistive load that is powered by an input AC voltage waveform. The computer program product includes first computer code configured to set a desired power operating level for the load. The computer program product also includes second computer code configured to receive a setting signal output from the first computer code that is indicative of the desired power operating level for the load, the second computer code further configured to determine a phase delay to be provided to an output AC voltage waveform that is to be provided to the load, and to output a control signal as a result thereof. The computer program product further includes third computer code configured to provide a control signal to an active element provided between a line that provides the input AC voltage waveform and the load, the active element receiving the control signal and turning off and on at predetermined times in accordance with the control signal, so as to create the output AC voltage waveform from the input AC voltage waveform. The control signal is provided based on the phase delay determined by the second computer code and the setting signal output by the first computer code.
According to yet another aspect of the invention, there is provided an energy savings device for an inductive or resistive load that is powered by an input AC voltage waveform. The energy savings device includes setting means for allowing a user to set a desired power operating level for the load. The energy savings device also includes processing means for receiving a signal from the setting unit indicative of the desired power operating level for the load, and for determining a phase delay to be provided to an output AC voltage waveform that is to be provided to the load, and to output a control signal as a result thereof. The energy savings device further includes signal conversion means, provided between a line that provides the input AC voltage waveform and the load, for receiving the control signal and turning off and on at predetermined times in accordance with the control signal, so as to create the output AC voltage waveform from the input AC voltage waveform.